Method for supplying an internal combustion engine with conditioned combustion gas, device for carrying out said method, method for determining the quantities of pollutants in the exhaust gases of an internal combustion engine, and device for carrying out said method

ABSTRACT

The invention relates to a method for supplying an internal combustion engine with conditioned combustion gas, involving the supply of humidity and/or temperature-conditioned combustion gas. The aim of this method is to largely enable the combustion air to be reliably and constantly conditioned even in dynamic operating conditions. To this end, an essentially constant and fully conditioned quantity of combustion gas is provided at each instant, the quantity corresponding to at least the maximum quantity required by the respective internal combustion engine. The invention also relates to a method for determining the quantities of pollutants in the exhaust gases of an internal combustion engine by diluting the exhaust gases using a diluent gas of a known composition. In order to enable the exhaust gases to be diluted in a precisely defined manner, and thus to precisely determine the quantities of pollutants, simply and reliably, an essentially constant and fully conditioned quantity of humidity and/or temperature-conditioned combustion gas is supplied at each instant, the quantity corresponding to at least the maximum quantity required by the respective internal combustion engine, and the exhaust gases are diluted with the quantity of combustion gas which is not used by the internal combustion engine. The invention also relates to devices for carrying out the two methods cited, each comprising a supply line ( 15 ) to the internal combustion engine ( 1 ), for the humidity and/or temperature-conditioned combustion gas, at least one measuring point ( 30 ) for determining the concentration of pollutants, and a determination device ( 32, 33; 41, 42 ) for the flow of a gas, said determination device comprising a passage ( 15 ) for a diluent gas of a known composition. the devices are characterized in that the supply line or supply passage ( 15 ) is designed for at least the maximum quantity of combustion gas required by the respective internal combustion engine ( 1 ), and a suction pipe ( 2 ) which can be connected to the internal combustion engine ( 1 ) branches off from the supply line ( 15 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for supplying an internal combustionengine with conditioned gas, particularly air, preferably on testbenches, including the supply of humidity and/or temperature-conditionedgas to the internal combustion engine, as well as a device to carry outthis method. The invention also relates to a method for determining thequantities of pollutants in the exhaust gases of an internal combustionengine, including the determination of the pollutant concentration andthe quantity of the following exhaust gas whereby dilution of theexhaust gas takes place by using a diluent gas of known composition. Theinvention also relates to a device to carry out this additional method.

2. The Prior Art

The condition of the intake air influences the operating behavior of aninternal combustion engine to a great extent. For example, the enginetorque increases in gasoline engines with increasing atmosphericpressure by approximately +0.12% per hectopascal. A temperature increaseof the drawn-in ambient air by 1° C. causes in the same case a loss ofpower of approximately −0.5%, for example. The humidity content of theintake air has only minor direct influence on engine power; however, theconsequences relative to exhaust gas emission is not to be disregarded,particularly nitrogen oxide, which can be the case in gasoline enginesas well as in diesel engines. A higher humidity content of the intakeair makes additionally possible in gasoline engines an earlier ignitiontime up to the point of the knocking limit, which has to be consideredduring tuning operation at the engine test bench.

Since the development of internal combustion engines places requirementsthat are becoming continuously higher relative to the ability toreproduce and the accuracy in test results, and based on exhaust gasregulations becoming more stringent worldwide as well as the higherpower density, it is therefore necessary to eliminate all influences asmuch as possible which effect the test results in the development ofengines. Since the intake air is also part of these influences, it isnecessary to condition the same to obtain comparable test conditions atthe test bench.

Known systems for conditioning of the intake air for internal combustionengines are available commercially (e.g. Combustion Air ConditioningUnit of the firm AVL-List GmbH, Graz, Austria or FEV AirCon of the firmFEV Motortechnik GmbH, Aachen, Germany). However, these systems aredirectly connected to the air supply system of the internal combustionengine and they must follow in this way the changes of the operatingcondition of the internal combustion engine and the resulting change ofairflow rate, and these systems must also follow thereby directly thechanges of the rate of airflow of the internal combustion engine itself.

The maximum rate of airflow in a gasoline engine is about 40 times theminimum rate of airflow. It is therefore understandable that duringrapid dynamic changes of the rate of airflow in a combustion engine,known systems can follow these changes only to a limited degree and onlya poor control quality of the conditions in the air is obtained duringthe dynamic changes in the rate of airflow. An example for a knownsystem of this type is described in DE 40 15 818 C2.

In DE 25 36 047 A1 is described, in contrast, a pure negative pressuresimulation while no steps are taken for complete conditioning of thecombustion air. Furthermore, there is a box provided in the discloseddevice into which enters the combustion air intended for combustion inthe internal combustion engine together with the exhaust gas of theengine, and wherein they may be combined or influence one anotherwhereby conditioning (of the air) is made almost impossible underreliable and constant conditions. The risk of mixing of combustion airwith exhaust gas is very great, especially in highly dynamic operatingconditions in a device such as the one disclosed in DE 25 36 047 A1,based on pressure pulsation, wide-reaching turbulence, thermal gradientsetc. In addition, the combustion air is drawn into said box depending onthe demands of the engine, which does almost never allow thecarrying-out of constant conditioning as well.

The first object of the invention is to avoid these and otherdisadvantages of the traditional conditioning method and conditioningdevices, and to make possible, to a great extent, reliable and constantconditioning of the combustion air even under dynamic and highly dynamicoperating conditions.

An additional subject area in the field of engine-testing technology isthe exhaust gas measuring technology by which there is to be determinedthe existing pollutant quantities from the measurable pollutantconcentrations in the exhaust gas of the engine. For this calculation isnecessary the quantity (mass) of the flowing exhaust gas from which theexhaust gas sample has been taken. This has to be measured eitherdirectly or it can be determined with the use of the subsequent balanceof the mass flows: supplied air mass+supplied fuel mass=dischargedexhaust gas mass. The supplied fuel mass can thereby be measured highlyaccurate and dynamically. Relative to the term “pollutant quantity”, itis to be noted that the subject matter is almost exclusively pollutantmass in the standards and guidelines for exhaust gas analysis. Sensorsto determine pollutants in a gas flow measure in general the pollutantconcentration, which means the quantity of pollutants—practicallyexclusively the pollutant mass (e.g. in milligrams)—relative to areference quantity of gas (mass or volume under actual or under standardconditions). The measured concentration at the measuring point has to bemultiplied by the corresponding flow quantity (mass flow or volumeflow).

A simple system for the accurate use of the balance equation isestablished when either the flow of the supplied air or, especiallyadvantageously, the flow of the discharged exhaust gas is kept constant.This occurs, for example, in the exhaust gas testing technology with theso-called CVS systems (constant volume sampling), which are standardizedand which are established accurate devices for the determination ofpollutant quantities in the exhaust gas. High dilution factors aregenerally required for the CVS systems. Extremely low pollutantconcentrations are created especially in low-pollution engines as aresult thereof, which can almost not be detected any longer by theanalyzers. An alternative to the CVS system for the determination ofpollutant quantities is now the analysis of the undiluted orcomparatively minor diluted exhaust gas in combination with the directmeasuring of either the incoming flow of air mass or, especiallyadvantageous, the flow of exhaust gas mass. However, this method couldnot be carried out properly up to now since the sensors needed for thispurpose have various inherent faults. Among other things, the highdynamic of engine operation and the strong flow pulsation as well as thepressure pulsations overriding the average flow are detected onlyinsufficiently and the sensors are, in general, not sufficiently suitedfor the hot and corrosive exhaust gases. For the solution of theseproblems were proposed suppression chambers and flow-measuringarrangements for the average flow, which have to be built, however,having very large dimensions, which are very difficult to be used on theengine and which oftentimes falsify the conditioned operating conditionsof the engine.

It was therefore another object of the invention to provide a method anda device which make possible a precisely defined dilution of the exhaustgas and thus a precise determination of the quantities of pollutants ina simple and reliable manner.

SUMMARY OF THE INVENTION

The firstly mentioned object relative to the conditioning of thecombustion gas is achieved according to the invention in that anessentially constant and fully conditioned quantity of combustion gas isprovided at each instant whereby said quantity corresponds to at leastthe maximum quantity required by the respective internal combustionengine. Through this measure, conditioning does not have to be performedagain dynamically, but the engine on the test bench has branches (in thesupply line) for the maximal required quantity of combustion airdiverting the quantity of combustion air needed for the actual operatingconditions, respectively. The conditioning system disposed upstream(from the engine) has to be designed nevertheless for the maximumquantity of combustion air whereby a constant flow of mass passesthrough the conditioning path in the case of the invention and wherebycontrol is made correspondingly simple.

According to an advantageous additional characteristic of the invention,it is proposed that the combustion gas not used by the internalcombustion engine bypasses the internal combustion engine and is thenmixed with its exhaust gas. It is made possible thereby in a simplemanner to obtain a small and a roughly adjustable pressure differentialin the system between the branching-off point of the combustion airactually needed by the engine and the discharge port of the exhaust gas,and thereby is also ensured a substance separation of combustion air andexhaust gas.

A simply realizable negative pressure control of the system can beachieved if the combustion air/exhaust gas mixture downstream from theengine is suctioned out, preferably with a defined negative pressurerelative to the atmospheric pressure.

Otherwise, there can be proposed alternatively or additionally that thecombustion gas is delivered to the internal combustion engine underincreased pressure relative to the atmospheric pressure—or unneededcombustion gas is diverted to bypass the internal combustion engine.

It is advantageously proposed thereby that between the conditionedcombustion gas and the exhaust gas or the combustion gas/exhaust gasmixture there is set a pressure drop, downstream from the internalcombustion engine, between 0.3 and 5 mbar, preferably between 0.5 and 3mbar.

It is made possible thereby to condition (the gas) to pressures betweenat least−300 mbar and +300 mbar on the intake-side as well as on theexhaust-side of the engine. This is achieved through a type of CVSmethod with at least a small excess of combustion gas of at leastapproximately 1.2 times the maximum quantity needed by the engine. Thesmall drop in pressure also ensures that the intake as well as theexhaust of the internal combustion engine, or systems disposed upstreamor downstream, are kept essentially on equal pressure level for correctnegative or positive pressure simulation. The actual value measurementfor pressure control occurs preferably at the intake section of theengine, which means that the pressure at the port of the engine exhaustsystem follows the pressure at the intake section within the predefineddrop in pressure.

According to an additional advantageous characteristic of the invention,it is proposed that the flow is kept essentially constant, independentfrom the absolute pressure. With “flow”, it could mean here and in thefollowing text, a flow of mass as well as a flow of volume as a flowingquantity. At constant flow, there are possible large and possiblydynamic pressure fluctuations by keeping the small control effort forthe conditioning of gas and the correspondingly simple design of thesystem is thereby made possible. Diverse known devices may be employedto keep the flow of combustion gas (air) constant or of other gasesdeveloping subsequently, such as (diluted) exhaust gas. Roots blowers orsimilar gas moving devices can be employed which move a constant gasvolume per working stroke or rotation so that the flowing mass isdependent on the pressure and temperature of the gas, the working strokefrequency, or the speed of rotation. Critical nozzle(s) or Venturitube(s) among others, can be provided having a gas moving device(suction fan) downstream in which the quantity of flowing gas isdetermined by the size of the cross section of the respective mostnarrow section in the nozzle(s) and the therein resulting sonicvelocity. This means, that the flowing volume and the flowing mass areonly dependent on the pressure and temperature of the gas upstream fromthe nozzle—but not on the pressure downstream from the nozzle. Anadditional embodiment of a device to keep the flow constant would beuncritical nozzles in which the dependency on backpressure is consideredthrough a respective measuring and control technology. All such devicesto keep the flow constant must be calibrated in the rule. The flow ofinterest (e.g. flow of mass or flow of volume under actual or understandard conditions) is then determined by the corresponding calibrationfactor of the device and by the pressure and temperature of the gas(air) upstream from the device.

In order to improve high-altitude simulation even more, it is proposedaccording to an additional characteristic of the invention that thedirect ambiance of the internal combustion engine is kept at the samepressure as the pressure of the conditioned combustion gas. The samecondition exists thereby all over in the area of the internal combustionengine, which makes the simulation substantially more accurate on thetest bench at the respectively desired sea level.

The internal combustion engine is advantageously surrounded by a flow ofconditioned combustion gas whereby it is made possible to use the intakeair in this way also as realistic ambient air of the motor, particularlyrelative to temperature. However, attention must be paid that sufficientair is moved through the bypass line so that no improper temperaturesdevelop, particularly temperatures that are too high. For example, itcan be advantageous in case of possibly provided gas-moving devices orpossibly connected exhaust gas measuring equipment, if the diluent gasfed into the exhaust gas is not hotter than 30° C., preferably nothotter than 25° C. On the other hand, condensation of the containedwater vapor should not occur in the undiluted nor in the diluted exhaustgas. For this reason, one has to pay attention that the temperature ofthe diluted exhaust gas is not too low—or that it does not drop below50° C., for example. Depending on the type of application, it couldtherefore be necessary to separately adjust the temperature of the gasin the supply line, e.g. by means of an additional heat exchanger.

The second object based on the invention is achieved in accordance withthe characteristics essentially mentioned above in that an essentiallyconstant and fully conditioned quantity of humidity and/ortemperature-conditioned combustion gas is supplied to the internalcombustion engine at each instant whose quantity corresponds to at leastthe maximum quantity required by the respective combustion engine, andwhereby the exhaust gas is diluted with the quantity of combustion gasthat is not used by the internal combustion engine. The novel system canthereby be employed advantageously in the exhaust gas testing technologyin which it is used for defined diluting of the exhaust gas. The lowexcess of combustion gas needed for conditioning of at leastapproximately 1.2 times the maximum quantity required by the engine isin most cases set too low for CVS systems—even if there is only a lowrequirement on precision demanded relative to the precision formeasuring the pollutant quantities—and said quantity of excesscombustion gas should thereby be greatly increased, in general. Ittherefore proposed to provide excess in-flowing conditioned combustiongas in the range of at least 4 to 10 times the quantity required by theengine to be used for diluting the exhaust gas of the internalcombustion engine.

The valves for the flowing quantities (mass) are necessary to determinenow the concentration of the pollutant quantity measured in the exhaustgas that is actually discharged by the internal combustion engine.According to the first embodiment variation of the invention, it isthereby proposed to keep constant the flow of the discharging gas andthe flow of exhaust gas diluted by the quantity of unused combustion gasand to determine the quantity of combustion gas supplied to the internalcombustion engine as well as the quantity of fuel.

Since the determination of essentially constant values is very simple,it can thereby be proposed that the flow of discharging exhaust gas,diluted by the unused quantity of combustion gas, is kept constant andis defined.

Alternative to the above object, it is nevertheless possible todetermine the quantity of pollutants in that the flow of the suppliedcombustion gas is kept constant, and its quantity and the quantity offuel supplied to the internal combustion engine is determined as well.

The flow of the supplied combustion gas is thereby kept advantageouslyconstant and the flow of the diluted exhaust gas is determined as well.This variation occurs preferably with a relatively minor diluted exhaustgas and it has the advantage that requirements for the flow sensor areconsiderably lowered since in this case, there is, on one hand, a nearlyconstant flow of exhaust gas mass and, on the other hand, the exhaustgas pulsates less, is not hot, and is less corrosive as a result of thediluted (thinned) air.

According to an additional characteristic of the invention, it isproposed that the determination of pollutant concentration occurs in theexhaust gas, which is diluted with the quantity of combustion gas notused by the internal combustion engine. Applicable are here also thefacts mentioned above relating to the flow sensor and relating to thesensor or the sampling device for pollutant concentration.

According to an additional embodiment example of the invention, thedetermination of the pollutant concentration can, of course, occur alsoin the undiluted exhaust gas and the determination is there more directand more correct relative to possible other substances carried along inthe diluent gas.

If a direct measurement of the pollutant concentration is necessary, itcan be proposed that the pollutant concentration in the availablecombustion gas is determined in addition. This value can be consideredin the determination of the quantity of pollutants emitted by theinternal combustion engine.

In the method for the determination of the quantity of pollutants, iscan be advantageously proposed that the quantity of available combustiongas is a multiple of the maximum quantity required by the combustionengine.

The determination of pollutant emission is also necessary at differentsea-level conditions and/or environmental conditions so that thissimulation can be provided here also in that the combustion gas/exhaustgas mixture downstream from the internal combustion engine is moved bysuction, preferably by a defined negative pressure relative to theatmospheric pressure—or that the combustion gas is delivered to theinternal combustion engine through increased pressure relative to theatmospheric pressure or whereby unneeded combustion gas bypasses theinternal combustion engine.

In each case it is thereby again of advantage if there is set a pressuredrop between 0.3 and 5 mbar, preferably between 0.5 and 3 mbar, betweenthe conditioned combustion gas and the exhaust gas or the combustiongas/exhaust gas mixture downstream from the internal combustion engine.

In the determination of pollutants in the exhaust gas, the flow is keptadvantageously and essentially constant, independent from the absolutepressure.

Precise simulation of various sea-level conditions and/or environmentalconditions may also be achieved through the method of exhaust gastesting if the direct ambiance of the internal combustion engine is keptat the same pressure as the pressure of the conditioned combustion gas,or if a flow of conditioned combustion gas surrounds the internalcombustion engine.

Attention must be paid thereby, particularly during the use of negativepressure for high-altitude simulation, that the respective measuringdevice is also under the ambient air pressure; however, these measuringdevices are generally not designed for an exhaust gas pressure of downto −300 mbar. It is therefore to be proposed that the negative pressureexisting during exhaust gas analysis must be compensated with anadditional pump. In measuring with the CVS system, double dilution isnot permissible in the LD range. The following possibilities existtherefore in taking measurements: either diluted modal exhaust gastesting (analysis), however, exclusively with heated analyzers based onthe low dilution ratio, additional measuring of the (almost) constantairflow upstream from the branching-off point of the supply line to theinternal combustion engine—or, the entire system is to be enlarged insuch a manner that minimum dilution rates of rdil≧4 are achieved.

The first object stated in the beginning is also achieved according tothe present invention through a device to supply an internal combustionengine with conditioned combustion gas whereby said device comprises asupply line leading to the internal combustion engine for humidityand/or temperature-conditioned combustion gas, and possibly a blower inthe supply line, and said device is characterized in that the supplyline or supply passage is designed for at least the maximum quantity ofcombustion gas required by the respective internal combustion enginewhereby a suction pipe, which can be connected to the internalcombustion engine, branches off from said supply line. Beside theadvantages mentioned already above relative to the method, the describedinventive device with its supply line has the advantage that thereexists a good flow characteristic, which ensures for the combustion airin the engine that no backup-mixing of exhaust gases can take place andthat there is no change in the parameter of the conditioned combustionair.

According to an additional characteristic of the invention, an exhaustgas line, connectable to the internal combustion engine, joins thesupply line downstream from the branching-off point of the intake line.Thereby is offered the possibility of negative pressure control whilemaintaining all previously mentioned advantages.

In the inventive device are also advantageously provided elements forthe adjustment of a pressure differential in the range between 3.5 and 5mbar, preferably between 0.5 and 3 mbar, which are disposed between thebranching-off point of the intake line and the merging point of theexhaust gas line with the respective supply line. Thus, a reliablesubstance separation can be guaranteed between combustion air andexhaust gas for all operational conditions of the engine—from idling upto full power.

This effect can be obtained in the same way—or it can be additionallyguaranteed—if there are provided devices to ensure a minimum flow ratebetween the branching-off point of the intake line and the merging pointof the exhaust gas line, at least corresponding to the diffusion rate ofexhaust gas in the conditioned combustion gas.

Apart from the possibility of connecting the inventive device to acentral conditioning system, it is also possible to include conditioningwith the inventive device itself whereby, in this case, the devices foradjustment and control of the temperature and/or humidity are providedupstream from the branching-off point of the intake line in the supplyline leading to the internal combustion engine, e.g. gas coolers, misteliminators, gas heaters and vapor delivery lines, preferably havingvapor metering valves.

In one embodiment of the inventive device it is proposed that agas-moving device be provided to be able to conduct positive pressurecontrol whereby said gas-moving device is disposed upstream from thebranching-off point of the intake line and a control device is provideddownstream from the merging point of the exhaust gas line for the gasflow.

Otherwise, negative pressure control is possible if a control device forthe gas flow is provided upstream from the branching-off point of theintake line and a gas-moving device is provided downstream from themerging point of the exhaust gas line. Both of the above-mentionedcontrol variations can be used in combination, of course.

At least one heat exchanger is advantageously provided between theinternal combustion engine and the gas-moving device to avoiddifficulties in the design of the gas-moving device, particularly in theform of a centrifugal blower of a radial blower, whereby an exhaustgas/air mixture could develop during the operation of the system atgreat negative pressure and/or based on turbulence. Operation undernegative pressure is thereby possible, even up to approximately 500 mbar(which corresponds to approximately 6,000 meters above sea level.)

Relative to the choice of gas-moving devices, suitable types to beselected depend on the respective requirements. For example, there aretwo advantages in case of Roots blowers: On one hand, negative pressuresup to 550 mbar are no problem (this is necessary to ensure −500 mbar inthe suction pipe) whereas centrifugal blowers have a limit ofapproximately 450 mbar in the desired dimensions. On the other hand, thenegative pressure as well as the positive pressure can be controlled bymeans of a speed-controlled Roots blower and thus a butterfly valve isunnecessary at the end of the collecting box since the flow can berestricted by means of the Roots blower. However, a throttle valve isarranged for negative pressure operation after the conditioning path andupstream from the engine so that the conditioning path is not biased bygreat negative pressure.

The Roots blower moves a nearly constant volume flow at constant speed,independent from the air pressure. However, the air-mass flow changescorrespondingly to the changes in pressure. The throttle valve can becorrespondingly adjusted depending on the air pressure to keep theair-mass flow nearly constant in the conditioning path (theseadjustments are determined during operation and are forwarded to thecontrol device accordingly.) Pressure control occurs then through speedcontrol of the Roots blower (for instance, via PID(proportional-integral-differential) control devices.)

The disadvantage of the Roots blower lies in the maximum possibletemperature of the delivered gas mixture, which is limited toapproximately 50–60° C. Should there only be required negative pressuresof approximately 350 mbar, then one can resort to the centrifugal blowerthat can be operated at a temperature of up to approximately 150° C.

Control of quantity can be accomplished in a simple and reliable mannerif the control devices for the gas flow are designed in the form ofbutterfly valves.

A precision control valve may be provided thereby in an advantageousmanner parallel to the butterfly valves.

In addition, substance separation can be ensured if a gas-moving deviceis provided between the branching-off point of the intake line and themerging point of the exhaust line. The desired pressure differentialbetween the intake-side and exhaust-side of the engine can be adjustedor influenced through said gas-moving device.

According to an additional embodiment or in combination with one of theabove-described devices, substance separation may also be achieved inthat devices are provided for the laminarization of the flow in thesupply line, preferably at least between the branching-off point of theintake line and the merging point of the exhaust gas line.

An additional alternative to achieve this effect is to provide a shockdrag and/or a muffler in the supply line between the branching-off pointof the intake line and the merging point of the exhaust gas line.

For the simple and economical design of the system, highly dynamicevents should have no effects on the internal combustion engine—or itshould have only the smallest effects on the required quantity ofconditioned gas. According to an advantageous embodiment of theinvention, the device is characterized in that at least one of thegas-moving devices is in controlled communication with the oppositecontrol device, relative to the internal combustion engine, for the gasflow. A control concept can be realized thereby, which keeps the flowthrough the system essentially constant even under dynamic pressurechanges.

The moving capacity of the gas-moving device is thereby advantageouslyadjustable dependent on the position of the control device disposed onthe opposite side. If, for example, a throttle valve is adjusted to thechange of pressure operating in the system—or of a pressuresequence—then the speed of a gas-moving device designed as a centrifugalblower, for example, is matched in such a manner that the flow quantityof conditioned gas remains essentially constant, independent from theabsolute pressure.

It is proposed according to an additional characteristic of theinvention, that to make an engine test as real as possible underprecisely defined conditions, the distance between the branching-offpoint of the intake line and the merging point of the exhaust gas lineshould correspond substantially to the distance between the air filterintake and the end of the muffler system of the vehicle whose internalcombustion engine is supplied with conditioned combustion gas.

According to an additional characteristic of the invention, it isproposed that a closed space is provided to receive the internalcombustion engine whereby said closed space is connected to the sectionof the supply line between the branching-off point of the intake lineand the merging point of the exhaust gas line. The engine to be testedis thereby biased with the pressure existing in the connecting linewhereby said pressure influences the engine from the outside, which is agreat advantage, particularly in high-altitude simulation (low airpressure).

Advantageously there is provided a closed space to receive the internalcombustion engine in the section between the branching-off point of theintake line and the merging point of the exhaust gas line. This spaceformed by a closeable and sealable box, relative to the ambiance, can bea component of the engine test bench and can thereby remain on the testbench if another engine is to be tested on the (same) test bench.However, the box is advantageously a component of the pallet onto whichthe engine is installed and which is made for transporting andstabilizing the engine on the test bench.

For the achievement of the second object, which is based in substance onthe invention, there is provided a device to determine the quantities ofpollutants in the exhaust gas of an internal combustion enginecomprising at least one measuring point, for example a sensor orsampling device, for determination of the pollutant concentration, and adetermination device for the flow of gas whereby said determinationdevice is provided with a passage leading from the exhaust gas passageto the supply passage for a diluent gas of known composition. Accordingto the invention, this passage is characterized in that the supplypassage for the diluent gas is designed for at least the maximumquantity of combustion gas required by the respective internalcombustion engine and whereby an intake line (suction pipe), which canbe connected to the internal combustion engine, branches off from saidsupply passage. The determination device to determine the constant ornearly constant flow (mass or volume) of combustion gas (air) or of(diluted) exhaust gas can be realized in various known ways, forinstance with a flow sensor for the mass or volume flow, such as ahot-wire (thermal) or an ultrasound measuring system, or a measuringsystem for pressure and temperature of the gas, disposed directly infront of the device, to keep the flow constant whereby the calibrationconstant and possible other values of this device are considered in thedetermination of the flow (e.g. the speed of the Roots blower.)

The supply passage for the diluent gas is thereby advantageouslydesigned for a multiple of the maximum quantity of combustion gasrequired by the respective internal combustion engine.

According to an additional characteristic of the invention, themeasuring point to determine the pollutant concentration in the exhaustgas passage is arranged downstream from the merging point of the exhaustgas passage into the supply passage for the diluent gas, to lower therequirements for the sensor or sampling device and to employ said sensorwhere a nearly constant exhaust-gas mass flow exists, on one hand, andwhere, on the other hand, the exhaust gas pulsates less, is not as hot,and is less corrosive.

In contrast, a more precise measurement is possible with robust sensorsor instruments (since it is conducted in a direct manner) if themeasuring point for the determination of the pollutant concentration inthe exhaust gas passage is arranged upstream from its merging point intothe supply passage of the diluent gas.

An additional measuring point to determine the pollutant concentrationis advantageously provided in the supply passage for the diluent gas,upstream from the merging point of the exhaust gas passage into saidsupply passage, to be able to additionally consider the pollutant burdenof the diluent gas.

The same effects and advantages as mentioned above can be achievedrelative to the determination device for the flow of a gas, if saiddetermination device is arranged in the same section as the measuringpoint for the determination of the pollutant concentration.

According to an alterative embodiment of the inventive device, there isa determination device for the flow of gas provided in the supplypassage for the diluent gas and there is also advantageously provided ameasuring device for the fuel mass delivered to the internal combustionengine whereby these devices are provided to carry out a method todetermine the flow of mass of the exhaust gas with the use of a balanceequation of supplied combustion gas and supplied fuel quantity. However,both devices may also be provided as a single unit or in combination forcalibration or for checking the values detected directly by sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is to be described in more detail in the followingdescription with the aid of accompanying drawings.

FIG. 1 shows thereby schematically a system according to the inventionfor positive pressure operation and negative pressure operation.

FIG. 2 is an illustration according to FIG. 1 for positive pressurecontrol and negative pressure control without compensation for loss ofpressure.

FIG. 3 is an illustration according to FIG. 1 for positive pressurecontrol only.

FIG. 4 is an illustration according to FIG. 1 for negative pressurecontrol only.

FIG. 5 is an illustration according to FIG. 1 for highly precisenegative and positive pressure control.

FIG. 6 is a schematic illustration of a system according to theinvention with a test piece consisting of an engine provided with anintake section and an exhaust gas section.

FIG. 7 relates to FIG. 6 whereby the entire engine is disposed inside aclosed space.

FIG. 8 is a version of the system in FIG. 7 with the box as aflow-through part of the supply line.

FIG. 9 corresponds to FIG. 6 whereby measuring points or sampling pointsare provided for measuring pollutant quantities.

FIG. 10 is an embodiment of the invention corresponding to FIG. 9, butwith another arrangement of the measuring points or sampling points andthe sensors.

FIG. 11 is an embodiment according to FIG. 6 with yet anotherarrangement of the measuring points or sampling points and the sensors.

FIG. 12 illustrates an embodiment of the system according to theinvention wherein determination units are provided for the flow ofcombustion air and for fuel consumption.

FIG. 13 is an embodiment which makes possible the conditioning of theintake air and the simulation of the ambient pressure, particularlyhigh-altitude simulation, and it makes the analysis of exhaust gaspossible as well.

DETAILED DESCRIPTION OF THE INVENTION

The system according to the invention, having already an integratedconditioning path (as seen in the direction of the air flow) consists ofa dust filter 5 having an intake opening 4, a device for movement of air6, preferably a radial fan or a blower, a butterfly valve for negativepressure operation 7, and air cooler 8—preferably and air/cold-waterheat exchanger having a throughput of a cooling medium that isadjustable for cold water 9—a mist collector for condensate 10, as wellas an air heater 11 that is adjustable in its heating capacity by meansof a control device 12. A vaporizer 13 can be arranged to controlhumidity from which vapor can be metered into the main air passage 15via a vapor metering valve 14 to adjust the humidity. An absolutepressure sensor 16, a temperature sensor 17 and a humidity sensor 18serve to measure the condition of the air.

The conditioned air in these system components is moved through the mainair line 15 of the branching off point 19 between the main line 20 andthe intake passage 2 at a quantity that corresponds to the maximumquantity used by the engine. Thus, always the same quantity of incomingair is to be treated by the conditioning path 4 through 18 upstream,which makes the design extremely simple—particularly the conditioning.All changes in the operation of the engine to be tested can thereby beincluded as well, even all highly dynamic transition elements, and aconstant conditioned quantity of combustion air is supplied at eachinstant to the internal combustion engine 1. A small speed-controllableaxial fan 21 can be optionally arranged in the main passage 20 forcompensation of pressure loss or for adjustment of a precisely definedpressure differential between the intake passage 2 and the exhaust gaspassage of the engine 1, whereby said fan 21 is adjusted in its speedwith the aid of the controlling device 33 depending on the differentialpressure between the intake and discharge of line 20. Measuring of thisdifferential pressure is conducted with the differential pressure sensor22. The line 20 and the exhaust gas passage 3 of the internal combustionengine 1 run via a merging piece 23 into the air evacuation passage 24.A butterfly valve for positive pressure operation 25 is arranged at theend of said air evacuation passage 24. An air-moving device 26 fornegative pressure operation—preferably a radial fan or a blower—isdisposed upstream from the air evacuation opening 27 for the dischargeof the air-evacuation flow into the atmosphere or into the exhaust gassystem of the test bench. An additional heat exchanger could possibly bearranged between the internal combustion engine 1 and the air-movingdevice 26, preferably in the air evacuation passage 24, whereby thedesign of the air-moving device is simplified and the choice of possibleother types (of devices) is widened and problems are avoided through theexhaust gas/air mixture downstream from the combustion engine 1 and/orthrough the operation at great negative pressure (up to 350 to 400mbar.)

An electronic adjustment and control device 28 is provided for theoperation of the system and to set the desired air conditions into whichdevices there are integrated all necessary adjustment devices requiredfor the operation of the equipment and all control devices for pressure29 and 30, temperature 31 and humidity 32. Consideration wasadvantageously given so that the mass flow is kept essentially constant,independent from the absolute pressure. For this purpose, one of thegas-moving devices 6, 26, 21 at the equipment-side is in controllingcommunication with the opposite control device 7, 25, relative to thecombustion engine 1, for the gas flow. Since there were heretofore onlysmall, insignificant pressure changes demanded in the positive pressureoperation, this control concept is mainly of importance for the negativepressure operation for which the control 7, which is arranged upstreamfrom the internal combustion engine 1, is in controlling communicationwith the gas-moving device 25 disposed downstream from the internalcombustion engine 1. The transporting capacity of the gas-moving device6, 26, 21, which most often depends on the (rotational) speed, is setaccording the position of the control device that is designed mostly asa throttle valve.

The functioning mode of the method can be described with the aid of FIG.1 as follows:

The internal combustion engine 1 draws in the air mass flow ^(m&) _(in)required for combustion through the intake passage 2 and feeds said airmass flow to the combustion. The developing exhaust gas mass flow ^(m&)_(out) resulting from the combustion is subsequently discharged throughthe exhaust gas passage 3. It is the object of the method to adjust theconditions of the air at the intake port of the intake passage 2, whichmeans pressure, temperature and humidity, independent from ambientconditions. Moreover, the pressure at the discharge port of the exhaustgas passage 3 should match the pressure at the intake port of the intakepassage 2 to a great extent. The air path during operation of theinternal combustion engine on the test bench is thereby as follows:Based on the effect of the two air-moving devices 6, 26, a defined airmass flow ^(m&) _(L) is moved through the intake opening 4, through theair-moving device 6, the butterfly valve for negative pressure operation7, the air cooler 8, the mist collector 10, the air heater 11, and intothe main air passage 15. At the branching-off point 19 of the mainpassage 20 and the intake passage 2 occurs a separation of the air massflow ^(m&) _(L) into the main-passage air mass flow ^(m&) _(Bp) and intothe exhaust-gas air mass flow ^(m&) _(in). The bypass air mass flow^(m&) _(Bp) is moved by a speed-controllable axial fan for compensationof the pressure loss 21, and at the merging point 23 of the exhaust gaspassage, said air mass flow merges again into the main passage 20together with the exhaust-gas mass flow ^(m&) _(out) onto the evacuationmass flow ^(m&) _(Ex). Said evacuation mass flow ^(m&) _(Ex) is movedthrough the butterfly valve for positive pressure operation 25, theair-moving device for negative pressure operation 26 and through theevacuation-air opening 27 into the atmosphere or into the evacuation-airsystem of the test bench.

The following relationships can be cited based on the law of massconservation and continuity as interrelationship of individual air massflows or exhaust-gas mass flows:^(m&) _(in)=variable as function of the operational enginecondition.  (i)^(m&) _(out)=^(m&) _(in)+^(m&) _(Br)  (ii)whereby ^(m&) _(Br) is the mass flow of the fuel required forcombustion.

However, the following is true for the use of conventional liquid ofsolid fuels or a nearly stoichiometric or super-stoichiometriccombustion method:^(m&) _(Br)□^(m&) _(in)  (iii)

For example, in the use of commercial diesel fuel, the stoichiometricair requirement is 14.5 ^(kg air) _(/kg fuel) and true is therefore

-   -   ^(m&) _(Br)=^(m&) _(in)/14.5, which validates the above        mentioned (iii) interrelationship.

Based on (iii), a fuel mass flow can be neglected for a rough estimateof the mass flow and (ii) can also be stated as:^(m&) _(out)≈^(m&) _(in)  (iv)

The air mass flows ^(m&) _(L) and ^(m&) _(Ex), which exist at thecomponents to control air conditions, and thereby the decisive valuesfor the quality of control of the method can be stated for alloperational conditions of the internal combustion engine (1) as follows:^(m&) _(L)=^(m&) _(in)+^(M&) _(BP)  (v)and^(m&) _(Ex=) ^(m&) _(out)+^(m&) _(Bp)  (vi)by using (iv) in (v) and (vi) it can thus be stated:^(m&) _(L)≈^(m&) _(Ex)  (vii)

It is obvious thereby that the air mass flows ^(m&) _(L) and ^(m&)_(Ex), which are decisive for the control of the condition of the air,are nearly independent from the operational condition of the internalcombustion engine 1 and its dynamic behavior are therefore onlydependent on the design and the operating mode of the technologicalcontrol component. It is thereby apparent that dynamic changes canfollow the operating mode of the internal combustion engine. A change inthe operating mode of the internal combustion engine causes merely achange of temperatures and thereby a change in the density of the airmass ^(m&) _(Ex). These changes may also be compensated with this methodthrough the behavior of the control device; however, these changes maybe influenced by the general design parameter of the system to a greatdegree, e.g. the size of the air mass flow flows ^(m&) _(L).

The control of the conditions of the air flow ^(m&) _(L) and thepressure of the air mass flow ^(m&) _(Ex) is performed as follows:

Control of Pressure at Positive Pressure Operation:

If the desired air pressure is to be higher than the ambient pressure,the control of the air pressure is performed through pressure increaseand movement of the air mass flow flow ^(m&) _(L) by the air-movingdevice 6 in cooperation with the butterfly valves for positive pressureoperation 25. The air-moving device 6 is operated at constant speedwhereby the air mass flow is chosen to be at least equal, advantageouslyeven considerably greater, than the maximum air consumption of theinternal combustion engine 1. The pressure in the entire line system israised to the desired air pressure through throttling of the air massflow with the butterfly valve for positive pressure operation 25 fromthe discharge port at the air-moving device 6 to the butterfly valve forpositive operation. The position of the butterfly valve for positivepressure operation 26 is adjusted thereby via the electronic controldevice for the positive-pressure butterfly valve 30. The actual pressurein the pipe system is thereby measured by the absolute pressure sensor16 and it is converted into an electric signal proportional to thepressure. This signal is transmitted to the control device for thepositive-pressure butterfly valve 30 as actual signal. The controldevice 30 compares the actual signal with the reference variable desiredby the user and produces a reference signal for the positive-pressurebutterfly valve 26 whereby said reference signal is proportional to theposition of the butterfly valve. In this operating mode, the position ofthe negative-pressure butterfly valve 7 is completely opened to avoidundesired throttle effects at this valve. Control of Pressure atNegative Pressure Operation:

If the desired air pressure is to be lower than the ambient pressure,control of the air pressure is performed through throttling at thebutterfly valve for negative pressure operation 7 and through movementof the air mass flow ^(m&) _(L) by suction via the air-moving device fornegative pressure operation 26. The air-moving device 26 is operated atconstant speed whereby the air mass flow is again chosen to be at leastequal to the maximum air consumption of the engine 1, again preferablyeven considerably greater. Through throttling of the air mass flow withthe butterfly valve for negative air pressure 7, the pressure in theentire line system is lowered to the desired air pressure from thebutterfly valve for negative pressure operation to the suction-side ofthe air-moving device 26. The position of the butterfly valve fornegative pressure operation 7 is thereby adjusted by the electroniccontrol device for the negative-pressure butterfly valve 29. The actualpressure in the pipe system is thereby measured by the absolute pressuresensor 16 and it is converted to an electric signal proportional to thepressure. This signal is transmitted to the control device for thenegative-pressure butterfly valve 29 as actual signal. The controldevice 29 compares the actual signal with the reference variable desiredby the user and produces a reference signal for the negative-pressurebutterfly valve 7 whereby said reference signal is proportional to theposition of the butterfly valve. In this operating mode, the position ofthe butterfly valve for positive pressure 25 is completely opened toavoid undesired throttle effects at this valve.

Control of Temperature:

The adjustment of temperature of the air mass flow ^(m&) _(in) occurswith the aid of the effect of the air cooler 8 and the air heater 11.Heating or cooling of the air mass flow can occur according to thedesired nominal temperature. The actual temperature is measured by thetemperature sensor 17 and is converted to an electric signalproportional to the temperature. This signal is transmitted to thecontrol device for temperature 31 as actual signal. The control device31 compares the actual signal with the reference variable desired by theuser and it produces a steady reference signal to the control valve forcold water 9 or to the regulating device for the output of heat 12.Adjustment of the desired nominal temperature is performed therebythrough adjustment of the required cycling of a cooling medium throughthe air cooler and/or adjustment of the required heat output of the airheater. Operational conditions could develop that require cooling andsubsequently heating as well (see also control of humidity.)

Control of Humidity in Air:

Adjustment of humidity of the air mass flow ^(m&) _(in) occurs with theaid of the effect of the air cooler 8 and through metering of vapor fromthe vapor generator 13. The air mass flow ^(m&) _(L) is cooled down inthe air cooler to below the dew point and is dried as a result of thethereby caused condensation of the humidity contained in the air flow.The developing condensate is collected during the flow through the mistcollector and is (subsequently) discharged. The adjustment of thedesired humidity occurs through metering of water vapor into the airflow of the main air passage 15. The actual humidity is measured by thehumidity sensor 18 and is converted to an electric signal proportionalto the humidity. This signal is transmitted to the control device forhumidity 32 as actual signal. The control device 32 compares the actualsignal with the reference variable desired by the user and produces asteady reference signal for the control valve for cold water 9 or forthe vapor metering valve 14 depending on the requirement for cooling(dehumidifying) or humidifying.

With the two above-mentioned control values is also the goal connectedto prevent condensation (of mainly water vapor) in the diluted exhaustgas. The temperature of the diluted exhaust gas must thus be higher thanits dew point, which is generally lower than 52° C. for the undilutedexhaust gas. Therefore, a heating device can be provided additionallyfor the combustion gas flowing through the main air passage 15. However,the exhaust gas of the internal combustion engine is most often muchhotter than the gas used to dilute the exhaust gas (namely thecombustion gas not required by the internal combustion engine 1) so thatthe diluted exhaust gas is heated up relative to the diluent gas and nocondensation develops in (almost) all cases—even without additionalheating.

Compensation for Pressure Loss in the Main Line:

A speed-controllable axial fan 22 can be arranged in the line 20 if itis necessary based on special requirements in the quality of pressurecontrol of the air mass flow in the exhaust gas passage. Pressure lossin line 20 is measured by the differential pressure sensor 22 andtransmitted as an electric actual signal to the speed-control device forthe axial fan 21. This setting of speed occurs in such a manner thatpressure loss is compensated in the main line 20 as illustrated in FIG.2.

If the control accuracy of the exhaust gas backpressure control allows,and there is allowed a small pressure differential to be set preciselybetween the intake passage 2 and the exhaust gas passage 3, one can doaway with speed-controllable axial fan for pressure loss compensation 21(see FIG. 1) as well as the control device for the axial fan 33.

Embodiment Variation for Pure Positive Pressure Operation:

FIG. 3 shows an embodiment variation that is suitable for pure positivepressure operation (relative to the ambiance.) In comparison to FIG. 1,this embodiment is illustrated by leaving off the components to generatethe negative pressure. In this embodiment are missing thereby thebutterfly valve for negative pressure operation 6 of FIG. 1, theair-moving device for negative pressure operation 26, as well as thecontrol device for the negative-pressure butterfly valve 29.

Embodiment Variation for Pure Negative Pressure Operation (FIG. 4):

FIG. 4 shows an embodiment variation that is suitable for pure negativepressure operation (relative to the ambiance.) In comparison to FIG. 1,this embodiment is illustrated by leaving off the components to generatethe positive pressure. In this embodiment are missing thereby thebutterfly valve for positive pressure operation 6, the butterfly valvefor positive pressure operation 25, as well as the control device forthe positive-pressure butterfly valve 30 of FIG. 1

Embodiment Variation for Highly Precise Air Pressure Control (FIG. 5):

FIG. 5 shows an embodiment of the invention wherein highly precise airpressure control can be realized, that is, for positive pressure as wellas for negative pressure. The butterfly valves 6, 25 used for settingthe positive pressure or the negative pressure are supplemented throughthe parallel employment of a respective precision-control valve 7 a, 25a, which is dimensioned clearly smaller in flow cross section that thebutterfly valves. In this case, setting of the desired air pressureoccurs in such a manner that rough adjustment of the air pressure isperformed in the beginning with the butterfly valve 7 or 25. Afterfalling below a defined control deviation relative to the actualpressure from the reference pressure, the position of these butterflyvalves 7, 25 is maintained and is not changed any more thereafter. Thefinal setting of the desired air pressure occurs subsequently thereofwith the aid of the precision-control valve 71 and 25 a.

This embodiment variation has the advantage that, on one hand, the airpressure can be brought very quickly near the desired value with the aidof the butterfly valves 7, 25—and, on the other hand, highly precisepressure control can be realized with the finely-tuned precision-controlvalves 7 a, 25 a.

In practice, it is especially advantageous if the conditions on the testbench correspond exactly to the conditions existing in the determiningoperation of the test piece, particularly in vehicle engines, whichmeans also the conditions of air filters, exhaust gas system etc.provided on the vehicle. As schematically illustrated in FIG. 6, thesupply line is therefore designed in such a manner that the length ofthe supply line 15 for the conditioned combustion air, between thebranching-off point 19 of the intake passage 2 to the internalcombustion engine 1 and the merging point 23 of the exhaust gas line 3is as long as the complete engine unit, including all components of theintake section upstream and the components of the exhaust sectiondownstream (of the engine), which means that the length between thebranching-off point 19 and the merging point 23 corresponds to thedistance between the air filter intake 1 a and the end of the mufflersystem 1 b of the vehicle.

FIG. 7 shows an additional advantageous embodiment of the system thatcorresponds in its basic design to the one in FIG. 6, except that theentire engine, including air filter 1 a, muffler system 1 b, intakepassage 2, and exhaust gas passage 3 are disposed in an closeable andsealable box 28 relative to the ambiance, and whose inner pressure isbrought to the pressure of the line 15 through line 29. FIG. 8 showsthat the box in FIG. 7 can be designed as a through-flowing section 28 aof line 15. It is possible thereby that the engine draws its intake airdirectly from this box so that the branching-off point 19 becomeslocated at the intake point of the engine 1, which means through theopen end of the intake passage 2. This of advantage since a pipe doesnot have to be connected to the intake point of the engine, whichnegatively influences the behavior of the intake section 1 a, 2 in somecases.

In the following is to be described the development of the inventivemethod or the device according to the invention relative to the exhaustgas testing technology whereby the existing quantities of pollutants inthe exhaust gas of the engine are to be determined from the measuredvalues of the pollutant concentrations. This is advantageously achievedin the present case by means of a so-called CVS (constant volumesampling) system, which is standardized and which has establishedprecise devices for the determination of the quantities of pollutants inthe exhaust gas. The specified high dilution factors can be reached bydiverting the exhaust gas of the internal combustion engine 1 into thecombustion gas not required for the combustion process and whichbypasses said engine. There is also made possible the precisely defineddilution of the exhaust gas with the conditioning of these combustiongases—and now also of the diluent gas at the same time—through theadvantageously possible combination and made possible is thereby aprecise determination of the quantities of pollutants in a simple andreliable manner.

For determination of the quantities of exhaust gas pollutants in themeasurable pollutant concentrations there can be measured the quantityof exhaust gas that either flows directly at the point of sampling—orthere will be used the mass balance equation (mass combustion air+fuelmass=exhaust gas mass), which has to be inevitably true for theinventive system consisting of the engine and the accompanying supplyand discharge passages for the combustion air or the exhaust gas. It isthereby especially advantageous if the mass flow of the dischargingexhaust gas is kept constant. This can be achieved through known meanssuch as a critical nozzle or a Roots blower.

The combustion air bypassing the internal combustion engine 1, which issubsequently used for dilution of the exhaust gas, should be a multipleof the maximum quantity of intake air of the engine so that the exhaustgas is diluted by the same quantity (or more) of diluent air. Agenerally known CVS system could also be retrofitted in an especiallyadvantageous manner and used for conditioning of the intake airaccording to the invention whereby the intake air of the motor is takenfrom the conditioned fresh air of the CVS system and the exhaust gas isfed to the exhaust gas diluting system as proposed in the CVS system.

The inventive system is advantageously employed to condition the intakeair to overcome the difficulties in measuring of the intake-air massflow or exhaust-gas mass flow for analysis of the more or less dilutedexhaust gas and said system is used for relatively minor dilutionwhereby the necessary flow measurement in the region of the supplied,conditioned intake air occurs still upstream from the branching-offpoint of the bypass line. This has the advantage that highly precisesensors can be employed for a nearly constanct and pulsation-free airflow even at dynamic operation of the engine.

For additional improvement in measuring the intake-air mass flow or theexhaust-gas mass flow for analysis of the more or less diluted exhaustgas, it is proposed that the inventive system is employed to conditionthe intake air and used for exhaust gas analysis with comparativelyminor dilution.

It may be furthermore proposed that in exhaust gas analysis, anadditional dilution system is used for employment after the relativeminor exhaust gas dilution by the inventive system, which allows apossibly required additional exhaust gas dilution. This can be ofadvantage especially when the necessary conditioning requirements differto a great degree from the operation of the engine and from theimportant dilution of exhaust gas.

A first embodiment example for a system to measure the quantities ofpollutants is illustrated in FIG. 9 whereby said system corresponds tothe one in FIG. 6 in its basic design, except that there is provided inline 24 a measuring point 30 for an exhaust gas analyzer 31 as well as ameasuring point 32 for a flow determination device 33. The determinationof flow is performed in line 24 with an exhaust-gas mass flow sensor,but in many cases determination will be sufficient using exhaust gaspressure sensors and temperature sensors under consideration of ancalibration factor and possibly additional signals of the unit 25, 26(e.g. the speed of a Roots blower), which signals can be transmitted viathe signal line 34 illustrated by a dotted line.

In some cases, for example during measuring of particle content andhydro carbon content in the exhaust gas of diesel fuel, the temperatureof the diluent air at point 23 must not drop below a certain limit, forinstance 50° C., since otherwise exhaust gas constituents may condenseand break down. It would therefore be necessary to provide a heatingelement (nor illustrated) in line 15 between points 19 and 23 thatsubsequently heats up the conditioned air in the conditioning system5-18 to the required diluting temperature. It could be possibly also benecessary for the protection of the intake fan to cool the exhaust gasfor exhaust gas analysis downstream from the measuring point. Anadditional measuring point 35 may advantageously be provided for thedetermination of the pollutant concentration of the diluent gas in thesupply passage 15, upstream of its merging point 23 into the exhaust gaspassage, preferably even upstream of the branching-off point 19 of theintake passage 2 leading to the internal combustion engine 1. A line 36leads from this measuring point 35 to the exhaust gas analyzer 31.

FIG. 10 corresponds to FIG. 9, except that one determination device 37is assigned not for the flow of diluted exhaust gas in 24 but for theentire quantity of air upstream from point 19. the unit 37 is preferablyagain a gas-mass flow sensor; however, in many cases determination willbe sufficient using gas pressure sensors and temperature sensors underconsideration of a calibration factor and possibly additional signals ofthe unit 5-18 (for instance, the speed of a Roots blower), whereby saidsignals can be transmitted by the signal line 38 illustrated by a dottedline. However, there is need here supplementary a determination unit 39for fuel consumption with a measuring point 40 on the engine 1 or in thefuel delivery system of the engine.

FIG. 11 corresponds to FIG. 6, except that the measuring point 30 for anexhaust gas analyzer 31 is arranged in the exhaust gas line 3 and servesalso for analysis of the undiluted exhaust gas. For conversion of thepollutant concentration to pollutant quantities is could be possiblydesirable to provide a measuring point 41 for a determination unit 42 todetermine the flow of the undiluted exhaust gas in line 3.

FIG. 12 corresponds to FIG. 11, except that determination units 42 areherein provided for the intake air of the engine with a measuring point43 in line 2 and for fuel consumption 39, 40 (similar to FIG. 10.)

FIG. 13 could be a preferred embodiment that makes possible, in anespecially advantageous manner, the conditioning of intake air andambient pressure simulation, particularly high-altitude simulation, aswll as exhaust gas analysis. It is shown that element 19 is designedhaving an enlarged, flow-through volume as part of line 15, which makespossible thereby free intake of the conditioned air through the intakesystem 2 and 1 a of the engine. This volume 19 is disposed within thebox 28 together with the intake system 1 and the engine 1 as well as theexhaust gas system 1 b whereby said box 28 is still in pressurizedcommunication with line 15 via line 29. This has the advantage that theexhaust gas analysis is not disrupted by possible vapors from the dirton the outside of the engine. Even so, it cannot be completely ruled outthat pollutants from said box enter the passage 15 through the pressureconnection line 29, even though box 28 has no cross flow of diluent airin this case. It can thereby be of advantage if, in contrast to FIG. 9,the measuring point 35 for possible existing pollutants of the diluentair are arranged in the passage 15 only downstream from the connectionpoint of line 29, for example, but still upstream of point 23, ofcourse. The measuring points 30 and 32 for flow and pollutantconcentration of the diluted exhaust gas are provided on line 24, justas in FIG. 9.

1. A device for supplying conditioned combustion gas to an internalcombustion engine comprising a supply line leading to the internalcombustion engine for humidity and/or temperature-conditioned combustiongas, wherein the supply line is capable of conveying the maximumquantity of combustion gas required by the internal combustion engineper unit of time when operating at full capacity, an intake line whichextends from said supply line for delivering said conditioned combustionair to said internal combustion engine at a branching off point.
 2. Adevice according to claim 1, wherein an exhaust gas line, connectable tothe internal combustion engine, joins the supply line downstream from abranching-off point of the intake line at a merging point.
 3. A deviceaccording to claim 2, including elements for the adjustment of apressure differential in the range between 3.5 and 5 mbar which aredisposed between the branching-off point of the intake line and themerging point of the exhaust gas line with the supply line.
 4. A deviceaccording to claim 3, including devices to ensure a minimum flow ratebetween the branching-off point of the intake line and the merging pointof the exhaust gas line, at least corresponding to the diffusion rate ofexhaust gas in the conditioned combustion gas.
 5. A device according toclaim 1, including devices for adjustment and control of the temperatureand/or humidity provided upstream from the branching-off point of theintake line in the supply line leading to the internal combustion engineincluding gas coolers, mist eliminators, gas heaters and vapor deliverylines.
 6. A device according to claim 2, including a gas-moving devicedisposed upstream from a branching-off point of the intake line and acontrol device downstream from a merging point of the exhaust gas line(3) for the gas flow.
 7. A device according to claim 2, including acontrol device for the gas flow is provided upstream from abranching-off point of the intake line and a gas-moving device isprovided downstream from the merging point of the exhaust gas line.
 8. Adevice according to claim 7, including at least one heat exchangerbetween the internal combustion engine and the gas-moving device.
 9. Adevice according to claim 8, wherein the control device for the gas flowis a butterfly valve.
 10. A device according to claim 9, including oneprecision control valve parallel to the butterfly valves.
 11. A deviceaccording to claim 10, including a gas-moving device between thebranching-off point of the intake line and the merging point of theexhaust gas line.
 12. A device according to claim 11, including devicesfor the laminarization of the flow in the supply line.
 13. A deviceaccording to claim 12, including a shock drag and/or a muffler in thesupply line between the branching-off point of the intake line and themerging point of the exhaust gas line.
 14. A device according to claim13, including at least one of the gas-moving devices is in controlledcommunication with the opposite control device, relative to the internalcombustion engine, for the gas flow.
 15. A device according to claim 14,wherein the moving capacity of the gas-moving device is adjustabledependent on the position of the control device disposed on the oppositeside.
 16. A device according to claim 15, wherein the distance betweenthe branching-off point of the intake line and the merging point of theexhaust gas line corresponds substantially to the distance between theair filter intake and the end of the muffler system of the vehicle whoseinternal combustion engine is supplied with conditioned combustion gas.17. A device according to claim 16, wherein a closed space is providedto receive the internal combustion engine and whereby said closed spaceis connected to the section of the supply line between the branching-offpoint of the intake line and the merging point of the exhaust gas line.18. A device according to claim 16, wherein a closed space is providedto receive the internal combustion engine in the section between thebranching-off point of the intake line and the merging point of theexhaust gas line.
 19. A method of supplying conditioned combustion gasto an internal combustion engine which, when operating at full capacity,consumes a certain maximum quantity of conditioned combustion gas perunit of time, comprising the step of continuously supplying at leastsaid certain maximum quantity of conditioned combustion gas per unit oftime for delivery to said internal combustion engine during operation ofsaid internal combustion engine.
 20. A method according to claim 19,comprising delivering a required quantity of conditioned combustion gasper unit of time to said internal combustion engine from at least saidcertain maximum quantity of conditioned combustion gas per unit of time,and wherein a remainder quantity of conditioned combustion gas is mixedwith exhaust gas emitted by said internal combustion engine to form anexhaust gas mixture downstream of said internal combustion engine.
 21. Amethod according to claim 20, including a step of applying negativepressure to said exhaust gas mixture to assist in downstream flow.
 22. Amethod according to claim 20, comprising the step of increasing thepressure of said required quantity of conditioned combustion gasdelivered to said internal combustion engine to a pressure aboveatmospheric.
 23. A method according to claim 20, comprising the step ofcreating a pressure differential between a higher pressure of theconditioned combustion gas and a lower pressure of the exhaust gasmixture of between 0.3 to 5 mbar.
 24. A method according to claim 20,comprising the step of maintaining a flow of conditioned combustion gasand exhaust gas mixture at an essentially constant rate.
 25. A methodaccording to claim 20, comprising the step of maintaining a pressure ofthe conditioned combustion gas at an ambient pressure of the environmentin which the internal combustion engine is located.
 26. A methodaccording to claim 20, comprising the step of directing conditionedcombustion gas to flow against and around said internal combustionengine.